1. Field of the Invention
The present invention relates to a process for the production of 4-hydroxystyrene (HSM), also known as paravinylphenol or p-vinyl phenol, by the deamination of p-.alpha.-amino- ethylphenol (AEP) (".alpha." means alpha herein).
2. Description of the Prior Art
4-Hydroxystyrene (HSM) is a well-known compound which is itself useful as a food flavoring substance and as an intermediate in the preparation of polymers and copolymers useful in coatings, electronic applications, ion exchange resins, photoresists, etc.
Although there are several known ways to prepare 4-hydroxystyrene, these known methods are not commercially feasible in the further utilization of the 4-hydroxystyrene. The 4-hydroxystyrene itself is difficult to isolate, since it (1) readily decomposes, (2) is toxic via skin absorption, and (3) readily polymerizes and as a result, those skilled in the art have made numerous attempts to find a method of synthesizing 4-hydroxystyrene in a manner which avoids polymerization and provides the 4-hydroxystyrene in a medium which can be utilized to prepare particular derivatives therefrom.
A preparation for 4-hydroxystyrene utilizing 4-acetoxystyrene is reported in a paper entitled "Preparation of Vinyl-phenols and Isopropylphenols", Corson et al., Volume 23, April 1958 J. Org. Chem. In this preparation, 4-acetoxystyrene is saponified in an aqueous system with a large concentration of a base, KOH, to produce an aqueous solution of the potassium salt of 4-hydroxystyrene which is neutralized with acid to precipitate 4-hydroxystyrene, As indicated above, the procedure is not practical or commercially feasible for production of large quantities of4-hydroxystyrene because the 4-acetoxystyrene and/or the 4-hydroxystyrene is not very stable and readily polymerizes under the aqueous saponification conditions employed therein, which involve high concentrations of soluble base, resulting in poor yields of 4-hydroxystyrene. Thus, a more efficient process for producing 4-hydroxystyrene is desired and needed.
The following prior art references are disclosed in accordance with the terms of 37 CFR 1.56, 1.97 and 1.93.
U.S. 5,087,772 (issued February 11, 1992) discloses the preparation of HSM by reacting 4-acetoxystyrene (ASM) with a suitable alcohol in the presence of a catalytic amount of a suitable base.
European Patent Application 0-128-984 (publication number) filed Aug. 30, 1983 discloses a process for the production of para-vinyl phenol (HSM) by dehydrogenation of para-ethyl phenol.
European Patent Application 0-108-624 (publication number) filed Nov. 4, 1983 discloses a process for the production of p-vinyl phenol polymer (polyhydroxystyrene polymer--PHS) by polymerizing p-vinyl phenol (HSM) in the presence of water and iron.
U.S. Pat. No. 4,032,5 13 (issued Jun. 28, 1977) discloses a process of producing PHS by cationically polymerizing HSM in the presence of a nitrile, such as CH.sub.3 CN, using a cationic polymerization initiator in a homogeneous reaction system.
All of the above cited prior art and any other references mentioned herein are incorporated herein by reference in their entirety.